1. Field of the Invention
The present invention relates to a display device capable of switching between a state in which an image is visible from one direction and a state in which the image is invisible from the one direction, while maintaining a state in which the image is visible from another specific direction. More particularly, the present invention relates to a display device suitable for a vehicle-mounted display device connected to a video signal output device (hereunder, referred to as “video device”) such as a navigation device or a DVD reproducing device.
2. Description of the Related Art
Vehicles are equipped with not only audio devices such as a radio and a CD player, but also video devices such as a navigation device, a television (TV) tuner, and a DVD reproducing device. Accordingly, the vehicles are also provided with display devices for displaying the images, such as a liquid crystal display panel and the like.
Currently, the vehicle-mounted display device tends to have a wider screen. In such a display device with the wide-screen, for instance, the screen is divided into two areas. In one of the areas is displayed a map image supplied by the navigation device, and in the other area is displayed images supplied by the TV tuner, the DVD reproducing device or the like. This kind of display device is capable of the so-called double-screen display (or multi-screen display).
However, for safety reasons, a driver is prohibited from watching the images of a movie, a TV and the like while the vehicle is traveling. For this reason, the currently used vehicle-mounted video device is designed so as not to display the images of the movie or the TV during the travel of the vehicle. Therefore, although a passenger riding in a front passenger seat is not prohibited from watching the movie, the TV and so on, he nevertheless is not able to watch them during the travel of the vehicle.